When an [[initramfs]] with the {{ic|base}} hook is used, which is the default, the {{ic|resume}} hook is required in {{ic|/etc/mkinitcpio.conf}}. Whether by label or by UUID, the swap partition is referred to with a udev device node, so the {{ic|resume}} hook must go ''after'' the {{ic|udev}} hook. This example was made starting from the default hook configuration.

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When an [[initramfs]] with the {{ic|base}} hook is used, which is the default, either the {{ic|resume}} hook, or the {{ic|systemd}} hook (which provides its own resume mechanism), is required in {{ic|/etc/mkinitcpio.conf}}. Whether by label or by UUID, the swap partition is referred to with a udev device node, so the {{ic|resume}} or {{ic|systemd}} hook must go ''after'' the {{ic|udev}} hook. This example was made starting from the default hook configuration:

Revision as of 01:42, 13 June 2015

Currently there are three methods of suspending available: suspend to RAM (usually called just suspend), suspend to disk (usually known as hibernate), and hybrid suspend (sometimes aptly called suspend to both):

Suspend to RAM method cuts power to most parts of the machine aside from the RAM, which is required to restore the machine's state. Because of the large power savings, it is advisable for laptops to automatically enter this mode when the computer is running on batteries and the lid is closed (or the user is inactive for some time).

Suspend to disk method saves the machine's state into swap space and completely powers off the machine. When the machine is powered on, the state is restored. Until then, there is zero power consumption.

Suspend to both method saves the machine's state into swap space, but does not power off the machine. Instead, it invokes usual suspend to RAM. Therefore, if the battery is not depleted, the system can resume from RAM. If the battery is depleted, the system can be resumed from disk, which is much slower than resuming from RAM, but the machine's state has not been lost.

Low level interfaces

Though these interfaces can be used directly, it is advisable to use some of high level interfaces to suspend/hibernate. Using low level interfaces directly is significantly faster than using any high level interface, since running all the pre- and post-suspend hooks takes time, but hooks can properly set hardware clock, restore wireless etc.

kernel (swsusp)

The most straightforward approach is to directly inform the in-kernel software suspend code (swsusp) to enter a suspended state; the exact method and state depends on the level of hardware support. On modern kernels, writing appropriate strings to /sys/power/state is the primary mechanism to trigger this suspend.

uswsusp

The uswsusp ('Userspace Software Suspend') is a wrapper around the kernel's suspend-to-RAM mechanism, which performs some graphics adapter manipulations from userspace before suspending and after resuming.

High level interfaces

Note: The end goal of these packages is to provide binaries/scripts that can be invoked to perform suspend/hibernate. Actually hooking them up to power buttons or menu clicks or laptop lid events is usually left to other tools. To automatically suspend/hibernate on certain power events, such as laptop lid close or battery depletion percentage, you may want to look into running Acpid.

Hibernation

In order to use hibernation, you need to create swap partition or swap file. See Swap for details.

About swap partition/file size

Even if your swap partition is smaller than RAM, you still have a big chance of hibernating successfully. According to kernel documentation:

/sys/power/image_size controls the size of the image created by the suspend-to-disk mechanism. It can be written a string representing a non-negative integer that will be used as an upper limit of the image size, in bytes. The suspend-to-disk mechanism will do its best to ensure the image size will not exceed that number. However, if this turns out to be impossible, it will try to suspend anyway using the smallest image possible. In particular, if "0" is written to this file, the suspend image will be as small as possible. Reading from this file will display the current image size limit, which is set to 2/5 of available RAM by default.

You may either decrease the value of /sys/power/image_size to make the suspend image as small as possible (for small swap partitions), or increase it to possibly speed up the hibernation process.

Required kernel parameters

The kernel parameter resume=swap_partition has to be used. Either the name the kernel assigns to the partition or its UUID can be used as swap_partition. For example:

resume=/dev/sda1

resume=UUID=4209c845-f495-4c43-8a03-5363dd433153

resume=/dev/mapper/archVolumeGroup-archLogicVolume -- example if using LVM

Generally, the naming method used for the resume parameter should be the same as used for the root parameter.

Hibernation into swap file

Warning:Btrfs does not support swap files. Failure to heed this warning may result in file system corruption. While a swap file may be used on Btrfs when mounted through a loop device, this will result in severely degraded swap performance.

Using a swap file instead of a swap partition requires an additional kernel parameter resume_offset=swap_file_offset.

The value of swap_file_offset can be obtained by running filefrag -v swap_file, the output is in a table format and the required value is located in the first row of the physical_offset column. For example:

Tip: The value of swap_file_offset can also be obtained by running swap-offset swap_file. The swap-offset binary is provided by package uswsusp-gitAUR.

Note:

The resume kernel parameter specifies the device of the partition that contains the swap file, not swap file itself! The parameter resume_offset informs the system where the swap file starts on the resume device.

If using uswsusp, then these two parameters have to be provided in /etc/suspend.conf via the keys resume device and resume offset.

Configure the initramfs

When an initramfs with the base hook is used, which is the default, either the resume hook, or the systemd hook (which provides its own resume mechanism), is required in /etc/mkinitcpio.conf. Whether by label or by UUID, the swap partition is referred to with a udev device node, so the resume or systemd hook must go after the udev hook. This example was made starting from the default hook configuration:

Troubleshooting

ACPI_OS_NAME

You might want to tweak your DSDT table to make it work. See DSDT article

VAIO Users

Add acpi_sleep=nonvs kernel flag to your loader, and you are done!

Suspend/hibernate doesn't work

There have been many reports about the screen going black without easily viewable errors or the ability to do anything when going into and coming back from suspend and/or hibernate. These problems have been seen on both laptops and desktops. This is not an official solution, but switching to an older kernel, especially the LTS-kernel, will probably fix this.

Wake-on-LAN

If Wake-on-LAN is active, the network interface card will consume power even if the computer is hibernated.